Granulocyte colony-stimulating factor (G-CSF) is a major regulator of granulocyte production. G-CSF is produced by bone marrow stromal cells, endothelial cells, macrophages, and fibroblasts, and production is induced by inflammatory stimuli. G-CSF acts through the G-CSF receptor (G-CSFR), which is expressed on early myeloid progenitors, mature neutrophils, monocytes/macrophages, T and B lymphocytes and endothelial cells. Mice deficient in G-CSF or the G-CSFR exhibit marked neutropenia, demonstrating the importance of G-CSF in steady-state granulopoiesis. However, G-CSF appears to be dispensable for emergency granulopoiesis, e.g., in response to an infection. G-CSF increases the production and release of neutrophils, mobilizes hematopoietic stem and progenitor cell, and modulates the differentiation, lifespan, and effector functions of mature neutrophils. G-CSF may also exert effects on macrophages, including expansion of monocyte/macrophage numbers, enhancement of phagocytic function, and regulation of inflammatory cytokine and chemokine production. G-CSF has also been shown to mobilize endothelial progenitor cells and induce or promote angiogenesis.
While G-CSF is used therapeutically, e.g., to treat neutropenia and/or mobilize hematopoietic stem cells, it also has negative actions in some conditions, e.g., inflammatory conditions and/or cancer. For example, administration of G-CSF exacerbates rheumatoid arthritis (RA), murine collagen-induced arthritis (CIA) and a passive transfer model of CIA in rats. G-CSF has been found in the serum and synovial fluid of RA patients. Furthermore, interleukin (IL)-1 and tumor necrosis factor α (TNFα), which are found at increased levels in patients suffering from RA, induce the production of G-CSF by human synovial fibroblasts and chondrocytes. Mice deficient in G-CSF are resistant to the induction of acute and chronic inflammatory arthritis.
G-CSF has also been shown to play a role in multiple sclerosis (MS). For example, G-CSF enhances adhesion of an auto-reactive T cell line model of MS to extracellular matrix as effectively as interferon γ and TNFα, which are known to exacerbate MS symptoms. Moreover, G-CSF deficient mice are resistant to development of experimental autoimmune encephalomyelitis (EAE).
G-CSF and G-CSFR have also been tied to cancer, with studies showing that this signaling pathway contributes to chemotherapy resistance, growth, survival, invasiveness and metastasis of various cancers. Moreover, G-CSF has been shown to induce to angiogenesis, a process important in the development of solid tumors.
It will be clear to the skilled person from the foregoing, that there is a need in the art for reagents that reduce the signaling of G-CSF through the G-CSFR. Exemplary agents will be suitable for use as therapeutics, e.g., to treat or prevent a G-CSF-mediated condition.